Three examples would be gamma rays (usually these rays are emitted from unstable isotopes and can be used in nuclear experiments and testing) ultraviolent rays that are emitted from the sun and can cause sunburn and even skin cancer because the rays mutate the DNA in the skin cells nucleus. And also X-Rays, microwaves, and radio waves, which is usually harmless because it isn’t enough radiation to mutate DNA in our cells
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Three of the four nitrogenous bases that make up RNA — adenine (A), cytosine (C), and guanine (G) — are also found in DNA. In RNA, however, a base called uracil (U) replaces thymine (T) as the complementary nucleotide to adenine (Figure 3). ... (Remember, DNA is almost always in a double-stranded helical form.)
Explanation:
I'm assuming this is a T or F question. The answer is F, because the mitochondria of an animal would produce vitamin D, so the answer is F.
Answer:
Physical
Explanation:
The skin is a physical barrier.
Mechanical barriers are made by mucous membranes
